Fructose oligosaccharides have nutritional advantages in animal and human diets. These oligosaccharides modify the relative proportions of intestinal bacteria and in particular are effective in increasing the proportion of bifido bacteria in the digestive tract of animals. Thus, products containing a high percentage of fructose oligosaccharides such as difructose dianhydrides, and higher oligomers derived therefrom, are in demand as nutritional additives.
In addition to disease and stress, the control of microflora is important in humans and especially animals. Microflora comprise bacteria found predominantly on the skin of animals and in the intestinal tracts. It is commonly believed that certain components of the normal intestinal microflora influence health and control of disease. The presence of microflora influences the point at which meat, milk and eggs will begin to spoil. Moreover, a large bacterial count is responsible for premature food spoiling.
Efforts to control disease caused by pathogenic microflora are expensive and sometimes ineffective, and add to the cost of producing meat, egg and milk products. Further, the administration of expensive antibiotics also adds to the costs of raising livestock. These costs are typically absorbed by the consumer.
Caramels are confectionery products obtained by heating reducing sugars such as glucose and sucrose. The time generally required to achieve caramelization is several hours, typically from 3 to 9 hours. The composition of caramels has been studied previously and caramels prepared from sucrose have been shown to contain small amounts of oligosaccharides, predominantly glucose disaccharides.
U.S. Pat. No. 5,318,794 and published PCT Applications WO94/27617 and WO94/27618 of the Applicant, disclose the production of caramels, e.g. sucrose oligosaccharides (STO), useful as bifidus factors, by pyrolysis of sucrose in the presence of small amounts of an organic acid such as citric acid. U.S. Pat. No. 5,206,355 discloses the heating of sucrose in a melt in the presence of an organic acid, e.g. citric acid, to form various trisaccharides and polymers.
Japanese Published Patent Applications JP 05168419 and AZ 930702 disclose difructose dianhydrides (DFDA) made by enzymic treatment of inulin, added to chicken feed (0.25 to 0.5%) to increase growth rates about 5-12% and decrease lipids 6-10% (Chem. Abs. 1994, 119, 159111).
Ponder et al. "Pyrolysis of Inulin, Glucose and Fructose", Carbohydrate Research, 244 (1993) 341-359, describes the pyrolysis of inulin. In Ponder et al., inulin was vacuum pyrolyzed for one hour at 240.degree. C. and treated with various basic additives such as sodium chloride, sodium hydroxide and calcium hydroxide. As reported on page 354 of that publication, difructose dianhydrides (DFDA's) were produced during the vacuum pyrolysis of inulin. However, the combined yields reported were very low.
The present invention provides a method for the pyrolysis of inulin to produce difructose dianhydrides, as well as trimers and higher oligomers thereof, in substantially greater yield than known previously. Further, the dianhydrides produced from the pyrolysis of inulin according to the invention have substantial nutritional advantages as bifidus factors.